A common use of grids is to show related data. Often it will be to expand details, or show some data related to the current row. A typical design pattern for this is the master-detail pattern. In a grid context, a grid row is the master, and then the detail can be shown in a number of ways. Sometimes it can be done by expanding a row; other times it might be to show details in a side panel (similar to e-mail readers such as Outlook that have a reading pane below or to the side of the list of e-mails).
We saw an example of the master-detail pattern with the DataView in Chapter 5, Working with Data, where we selected an employee and saw more details to the side. Similar techniques can be used with the GridPanel. This is because the row of data is held by the Store, which is common to the DataView and GridPanel. Here we will look at expanding a grid row as a way to show more details.